A vacuum processing apparatus produces fluorine radicals by activating a fluorinating gas containing at least fluorine atoms and fluorinates the surface of a component formed of an organic material (32) exposed to an atmosphere of a processing chamber (2) before carrying an object (S) into the processing chamber (2). The object (S) is carried into the processing chamber (2) after the completion of a fluorinating process. The object (S) is processed with a processing gas containing at least oxygen radicals. Etching of the component formed of the organic material (32) can be prevented by the fluorination of surface of the component formed of the organic material (32) and exposed to an atmosphere in the processing chamber (2).
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1. A vacuum processing method of processing at least one object to be processed with an oxygen radical in a processing chamber defined by a vacuum vessel of a vacuum processing apparatus, which comprises the steps of:
a) activating a fluorinating gas containing at least a fluorine atom and a gas containing at least an oxygen atom in a plasma producing chamber separated from the processing chamber for producing a fluorine radical; b) supplying the fluorine radical and the oxygen radical into the processing chamber, not yet containing said at least one object to be processed; c) fluorinating a surface of a component of the processing apparatus, said component being formed of an organic material and exposed to an atmosphere in the processing chamber with the fluorine radical; d) moving the at least one object to be processed into the processing chamber after the surface of the component has been fluorinated; and e) processing the at least one object to be processed with an oxygen radical produced by activating a process gas in the plasma producing chamber.
2. The vacuum processing method of
the vacuum processing apparatus comprises an object support table disposed in the processing chamber to support the at least one object to be processed thereon, and an electronic chuck mounted on a surface of the object support table to hold the at least one object to be processed thereon; the electrostatic chuck comprises an electrode, and an electrode covering sheet covering the electrode; and the organic material comprises a material forming the electrode covering sheet and an organic adhesive bonding the electrostatic chuck to the surface of the object support table.
3. The vacuum processing method of
the organic material comprises an organic adhesive to bond the protective sheet.
4. The vacuum processing method of
5. The vacuum processing method of
7. The vacuum processing method of
8. The vacuum processing method of
9. The vacuum processing method of
11. The vacuum processing method of
12. The vacuum processing method of
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This application is a continuation of International PCT application No. PCT/JP98/01949 filed on Apr. 28, 1998.
1. Field of the Invention
The present invention relates to a vacuum processing method using oxygen radicals for processing an object to be processed in a processing chamber defined by a vacuum vessel, and a vacuum processing apparatus for carrying out the same.
2. Description of the Background
Semiconductor wafers for fabricating ICs and glass substrates for liquid crystal displays, etc. (hereinafter referred to as "object to be processed" or "object") are processed by a process, such as an etching process or an ashing process, by a vacuum processing method using a vacuum processing apparatus. The vacuum processing method and the vacuum processing apparatus place an object in a processing chamber defined by a vacuum vessel and process the object in an evacuated atmosphere.
Conventional vacuum processing methods and apparatus for carrying out the same include a chemical dry etching (CDE) method and an apparatus for carrying, out the same which produce radicals in a plasma producing chamber separated from a processing chamber by activating a process gas, and introduce the radicals into the processing chamber to etch a thin film formed on a surface of the object placed in the processing chamber with the radicals.
Conventional vacuum processing methods and apparatus for carrying out the same further include a reactive ion etching (RIE) method and an apparatus for carrying out the same which produce a plasma by applying a radio-frequency voltage to a process gas supplied into a processing chamber, and etch an object placed in the processing chamber with the plasma produced in the processing chamber, and a microwave plasma etching method and an apparatus for carrying out the same which produce a plasma by exciting a process gas supplied into a processing chamber by applying a microwave to the process gas, and etch an object placed in the processing chamber with the plasma.
When an object is processed with oxygen radicals by the conventional vacuum processing method and the apparatus for carrying out the same, organic structural members and organic adhesives are etched if they are exposed to oxygen radicals in the processing chamber.
Referring to
The electrode covering sheets 30 are formed of a heat-resistant polymer, i.e., an organic material, such as a polyimide. The lower electrode covering sheet 30 is bonded to the support surface 3a of the object support table 3 with an organic adhesive 32.
Since the electrode covering sheets 30 and the adhesive 32 are formed of organic materials, portions of the electrode covering sheets 30 and the adhesive 32 exposed to an atmosphere in the processing chamber are etched by oxygen radicals for processing the object.
Since the components formed of organic materials and exposed to the atmosphere in the processing chamber are etched by oxygen radicals, the components of the vacuum processing apparatus, such as the electrostatic chuck, are short-lived and are sources of particles that reduces the yield of products. Essentially, the vacuum processing apparatus using oxygen radicals must avoid using organic materials. However, the use of parts formed of organic materials in such an vacuum processing apparatus is unavoidable in the present circumstances because of requirements for machining parts or for the common use of parts.
Accordingly, it is an object of the present invention to provide a vacuum processing method and an apparatus for carrying out the same capable of preventing the etching of parts formed of organic materials and exposed to an atmosphere in a processing chamber even when an object is processed with oxygen radicals.
According to the present invention, a vacuum processing method of processing an object to be processed with an oxygen radical in a processing chamber defined by a vacuum vessel of a vacuum processing apparatus comprises the steps of: fluorinating a surface of a component formed of an organic material and exposed to an atmosphere in the processing chamber with a fluorine radical produced by activating a fluorinating gas containing at least a fluorine atom with the vacuum processing apparatus before carrying the object into the processing chamber; carrying the object into the processing chamber; and processing the object with the oxygen radical produced by activating a process gas containing at least an oxygen atom.
The term `radical` as used in the description denotes a chemically highly active atom or molecule. Sometimes, radicals are referred to as `active species`.
Preferably, the vacuum processing apparatus comprises an object support table disposed in the processing chamber to support the object thereon, and an electrostatic chuck mounted on a surface of the object support table to hold the object on the object support table, and the electrostatic chuck comprises an electrode, and an electrode covering sheet covering the electrode. The organic material is that forming the electrode covering sheet and an organic adhesive bonding the electrostatic chuck to the surface of the object support table.
Preferably, the vacuum processing apparatus comprises an object support table disposed in the processing chamber to support the object thereon, an electrostatic chuck mounted on a surface of the object support table to hold the object on the object support table, and a protective sheet of a fluororesin covering the electrostatic chuck to protect the same. The organic material includes an organic adhesive used to bond the protective sheet.
Preferably, the fluorinating gas is a mixed gas including a gas containing at least a fluorine atom and an O2 gas.
Preferably, the gas containing at least a fluorine atom is one of CF4, C2F6, C3F8, NF3 and SF6, or a mixture of some of these gases.
Preferably, a ratio of a flow rate of the O2 gas to a flow rate of the fluorinating gas including the O2 gas is 40% or below.
Preferably, the process gas contains at least an O2 gas.
Preferably, the process gas and the fluorinating gas are activated in a plasma producing chamber separated from the processing chamber, and the fluorine radical or the oxygen radical is supplied into the processing chamber.
Preferably, the object processing step processes the plurality of objects successively, and the fluorinating step is performed after the object processing step, and the object processing step and the fluorinating step are repeated alternately.
The vacuum processing method according to the present invention fluorinates the component formed of organic material and exposed to the atmosphere in the processing chamber with the fluorine radical, and then processes the object with the oxygen radical. Fluorinated surface layer of the organic component serves as protective film to prevent the etching of the component formed of the organic material with an oxygen radical.
A vacuum processing apparatus according to the present invention comprises: a vacuum vessel defining a processing chamber to be evacuated; radical producing means for producing a fluorine radical by activating a fluorinating gas including at least a fluorine atom and for producing an oxygen radical by activating a process gas containing at least an oxygen atom; gas supply means for supplying the fluorinating gas or the process gas to the radical producing means; and an object support table disposed in the processing chamber to support an object to be processed thereon; wherein a surface of a component formed of an organic material and exposed to an atmosphere in the processing chamber is fluorinated by the fluorine radical, and then the object is mounted on the object support table and processed with the oxygen radical.
A vacuum processing apparatus according to the present invention comprises: a vacuum vessel defining a processing chamber to be evacuated; radical producing means for producing an oxygen radical by activating a process gas containing at least an oxygen atom; a gas supply means for supplying the process gas to the radical producing means; an object support table disposed in the processing chamber to support an object to be processed thereon; an electrostatic chuck mounted on a surface of the object support table to hold the object on the object support table; and a protective sheet formed of a fluororesin and covering the electrostatic chuck to protect the electrostatic chuck.
Preferably, a surface of a component formed of an organic material and exposed to an atmosphere in the processing chamber is fluorinated with a fluorine radical produced by activating a fluorinating gas containing at least a fluorine atom with the radical producing means.
Preferably, the fluorinating gas is a mixed gas including a gas containing at least a fluorine atom and an O2 gas.
Preferably, the gas containing at least a fluorine atom is one of CF4, C2F6, C3F8, NF3 and SF6, or a mixture of some of these gases.
Preferably, a ratio of a flow rate of the O2 gas to a flow rate of the fluorinating gas including the O2 gas is 40% or below.
Preferably, the process gas contains at least an O2 gas.
Preferably, the radical producing means has a plasma producing chamber separated from the processing chamber, and the radical produced in the plasma producing chamber is supplied into the processing chamber.
Preferably, a cycle of fluorinating a component formed of an organic material and exposed to an atmosphere in the processing chamber and successively processing a plurality of objects is repeated.
The vacuum processing apparatus according to the present invention fluorinates the surface of the component formed of the organic material and exposed to the atmosphere in the processing chamber with the fluorine radical, and then processes the object with the oxygen radical. The fluorinated surface layer of the component serves as protective film to prevent the etching of the component formed of the organic material with the oxygen radical.
The vacuum processing apparatus according to the present invention is provided with the protective sheet of a fluororesin covering the electrostatic chuck. Therefore, the etching of the electrostatic chuck with the oxygen radical can be prevented by the protective sheet covering the electrostatic chuck.
A vacuum processing method and an apparatus for carrying out the same embodying the present invention will be described hereinafter with reference to the accompanying drawings.
Referring to
The vacuum vessel 1 has a bottom wall 4 provided with gas outlet openings 5. Each of discharge pipes 6 has one end connected to a vacuum pump, not shown, and the other end connected to the outlet opening 5. The vacuum vessel 1 has a top wall 7 provided with a gas inlet opening 8. A gas supply pipe 9 formed of a fluororesin is connected to the gas inlet opening 8. A quartz pipe 10 has one end connected to the gas supply pipe 9 and the other end sealed by a sealing member 11 internally provided with a gas passage 19. A gas supply pipe 18 has one end connected to the sealing member 11 and the other end connected to branch pipes 20 and 21.
The branch pipes 20 and 21 are connected to a first gas cylinder 23 provided with a first flow regulating valve 22 and a second gas cylinder 25 provided with a second flow regulating valve 24, respectively. The first gas cylinder 23 and the second gas cylinder 25 constitute a gas supply source (gas supply means) 26.
The first gas cylinder 23 contains a gas containing at least fluorine atoms, preferably, one of CF4, C2F6, C3F8, NF3 and SF6, or a mixture of some of these gases. The second gas cylinder 25 contains a gas containing at least oxygen atoms, preferably, a gas containing at least O2 gas.
A plasma producing device (radical producing means) 13 provided with a waveguide 12 is combined with the quartz pipe 10 so as to surround a section of the quartz pipe 10. A plasma producing chamber 14 is formed in the section of the quartz pipe 10 surrounded by the plasma producing device 13. A microwave generator 27 is connected to the waveguide 12.
A shower plate 16 provided with a plurality of gas jetting holes 17 is placed in the processing chamber 2 so as to form a gas storage chamber 15 above the processing chamber 2 to distribute radicals supplied into the processing chamber 2 uniformly over the entire surface of the object S.
The electrostatic chuck 28 is covered with a protective sheet 31. Preferably, the protective sheet 31 is formed of a fluororesin. Since the electrode covering sheets 30 of an organic material are covered with the protective sheet 31, the erosion of the surfaces of the electrode covering sheets 30 by the etching action of oxygen radicals which are used for etching the object S can be processed.
The protective sheet 31 is bonded to the surface of the upper electrode covering sheet 30 of the electrostatic chuck 28 and to a peripheral region of the support surface 3a of the object support table 3 with the organic adhesive 32. The peripheral surface 33 of the layer of the organic adhesive 32 is exposed to an atmosphere in the processing chamber 2 (FIG. 1). Therefore, the peripheral surface 33 of the layer of the organic adhesive 32 is subject to erosion by etching while the object S is processed with oxygen radicals unless the some measures are taken to protect the peripheral surface 33.
Some parts of components formed of organic materials are exposed, for example, on the inner surface of the vacuum vessel 1 in addition to the peripheral surface 33 of the layer of the organic adhesive 32.
The vacuum processing method and the apparatus embodying the present invention evacuates the vacuum vessel 1 to a vacuum (reduced pressure) by removing gases and vapors through the outlet openings 5 and the discharge pipes 6 by the vacuum pump before carrying the object S into the processing chamber 2.
The gas containing at least fluorine atoms is supplied from the first gas cylinder 23 through the branch pipe 20, the gas supply pipe 18 and the gas passage of the sealing member 11 into the quartz pipe 10. At the same time, the gas contained at least oxygen atoms is supplied from the second gas cylinder 25. The first flow regulating valve 22 and the second flow regulating valve 24 are adjusted so that the gas containing at least fluorine atoms and the gas containing at least oxygen atoms are supplied at flow rates and flow rate ratios suitable for fluorinating the organic components.
Microwaves generated by the microwave generator 27 are guided by the waveguide 12 of the plasma producing device 13 into the plasma producing chamber 14. Consequently, glow discharge is generated in the plasma producing chamber 14 and a plasma P is produced, whereby fluorine contained in the mixed gas for fluorination is excited and fluorine radicals are produced.
The fluorinating gas containing fluorine radicals is supplied through the quartz pipe 10, the gas supply pipe 9 and the gas inlet opening 8 into the gas storage chamber 15. Then, the fluorinating gas is jetted from the gas storage chamber 15 through the gas jetting holes 17 so as to be uniformly distributed in the processing chamber 2 by pressure difference between the gas storage chamber 15 and the processing chamber 2.
Fluorine radicals thus supplied into the processing chamber 2 fluorinate, for example, the peripheral surface 33 of the layer of the organic adhesive 32, i.e., a surface of an organic component exposed to an atmosphere in the processing chamber 2. The fluorinating gas reacted with the peripheral surface 33 of the layer of the organic adhesive 32 is discharged through the gas outlet openings 5 and the discharge pipes 6 by the vacuum pump.
Such a fluorinating process is continued for a time necessary to form a fluorinated film of a desired thickness. Then, the supply of the gases from the first gas cylinder 23 and the second gas cylinder 25 is stopped, and the object S is carried into the processing chamber 2. Subsequently, the gas containing at least oxygen atoms is supplied through the branch pipe 21, the gas supply pipe 18 and the gas passage 19 of the sealing member 11 into the quartz pipe 10. At the same time, the gas containing at least fluorine atoms is supplied from the first gas cylinder 23. The first flow regulating valve 22 and the second flow regulating valve 24 are adjusted so that the gas containing at least fluorine atoms and the gas containing at least oxygen atoms are supplied at flow rates and flow rate ratios suitable for etching the object S.
Microwaves generated by the microwave generator 27 are guided by the waveguide 12 of the plasma producing device 13 into the plasma producing chamber 14. Consequently, glow discharge is generated in the plasma producing chamber 14 and a plasma P is produced, whereby oxygen contained in the process gas, i.e., a mixed gas of the gas containing at least oxygen atoms and the gas containing at least fluorine atoms, is excited and oxygen radicals are produced.
The process gas containing oxygen radicals is supplied through the quartz pipe 10, the gas supply pipe 9 and the gas inlet opening 8 into the gas storage chamber 15. Then, the process gas is jetted from the gas storage chamber 15 through the gas jetting holes 17 so as to be uniformly distributed in the processing chamber 2 by pressure difference between the gas storage chamber 15 and the processing chamber 2. Oxygen radicals thus supplied into the processing chamber 2 reacts with a thin film formed on a surface of the object S to etch the thin film by an etching process. The process gas reacted with the thin film formed on the surface of the object S is discharged through the gas outlet openings 5 and the discharge pipes 6 by the vacuum pump.
The oxygen radicals supplied into the processing chamber 2 reach, for example, the peripheral surface 33 of the layer of the organic adhesive 32, i.e., a surface of an organic component exposed to the atmosphere of the processing chamber 2. However, the etching of the peripheral surface 33 of the layer of the organic adhesive 32 and the like by the oxygen radicals is limited to the least unavoidable extent and are etched very little because the peripheral surface 33 of the layer of the organic adhesive 32 and the like are fluorinated beforehand.
The etching process stopped after successively etching several or several tens of objects S, and the fluorinating process is performed after removing the last object S from the object support table 3 to fluorinate the surfaces of the organic components again. Then, the etching process is resumed. Thus, the fluorinating process and the etching process are repeated alternately to process several or several tens of objects S successively after fluorinating the surfaces of the organic components.
Although the embodiment has been described as applied to the etching process for etching objects, the embodiment is applicable also to an ashing process.
Preferably, the fluorinating gas is one of CF4, C2F6, C3F8, NF3 and SF6, or a mixture of some of these gases.
Preferably, the process gas is a gas containing at least O2 gas.
Although the electrostatic chuck 28 of the vacuum processing apparatus in the foregoing embodiment is covered with the protective sheet 31, the present invention may be embodied by a vacuum processing method and an apparatus provided with the electrostatic chuck 28 not covered with any sheet corresponding to the protective sheet 31.
When the object support table 3 as shown in
Thus, the etching of the electrode covering sheet 30 and the surface of the layer of the organic adhesive 32 with oxygen radicals can be prevented in the etching process for etching the object S with oxygen radicals.
In
The result of experiments in which the sample wafer was subjected to the fluorinating process and the same etching process of the foregoing conditions is shown in a lower section in FIG. 3. The fluorinating process used a mixed gas containing three parts CF4 gas and one part O2 gas. The etching process used an etching gas containing one part CF4 gas and three parts O2 gas and microwaves of 700 W in power. The processing chamber was evacuated at 40 Pa and the object support table 3 was kept at 5°C C. for the fluorinating process. After the fluorinating process, the sample wafer was subjected to the etching process.
The carbon film was etched by a depth of only 0.5 μm, which proved the great effect of fluorination on the suppression of etching of the carbon film by oxygen radicals.
As obvious from
When the mixed gas containing CF4 and O2 is used as a fluorinating gas, a preferable O2/(O2+CF4) flow rate ratio is not greater than 40%.
As is apparent from the foregoing description, the vacuum processing method and the apparatus for carrying the same embodying the present invention fluorinate the surfaces of the organic components exposed to the atmosphere in the processing chamber 2 with fluorine radicals in the fluorinating process, and then etches the object S with oxygen radicals in the etching process. Therefore, etching of the organic components with oxygen radicals can be prevented.
Since the electrostatic chuck 28 is covered with and protected by the protective sheet 31 of a fluororesin, etching of the electrode covering sheets 30 of the electrostatic chuck 28 with oxygen radicals can be prevented.
Since the fluorinating process for fluorinating the organic components can be achieved by the vacuum processing apparatus, any special apparatus for the fluorination of the organic components is unnecessary, and the members requiring fluorination by the fluorinating process need not be removed from the vacuum processing apparatus.
The present invention is not limited in its practical application to the foregoing CDE method and the CDE system, and is applicable to various vacuum processing methods and vacuum processing apparatus which process objects in a vacuum atmosphere. More concretely, the present invention is applicable to dry etching methods and apparatus for carrying out the same, such as reactive ion etching (RIE) methods and apparatus for carrying out the same and microwave plasma etching methods and apparatus for carrying out the same, or ashing methods and apparatus for carrying out the same.
The present invention can be applied to an etching/ashing process for etching/ashing semiconductor wafers for fabricating ICs and glass substrates for liquid crystal displays.
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